Electrostatic printer

ABSTRACT

An electrostatic printing machine having an exposure station and an imaging station, and having copy sheet supply means for the storage of photoductive copy sheets, means for moving a copy sheet from said supply means and past the imaging station, and vacuum means for holding the copy sheet at the image station. The machine includes stop means for uncoupling drive means, and brake means for stopping the movement of the means for moving the copy sheet past the imaging station. The machine also has a plurality of copy paper sheet magazines from which copy sheets may be selectively supplied.

United States Patent Mihojevich et a1. 1 1 Oct. 17, 1972 [54]ELECTROSTATIC PRINTER [56] References Cited [72] Inventors: StevenMihojevich, Northbrook; UNITED STATES PATENTS rf Elk h Arthur 82,295,055 9/1942 Rupp et a1. ..271/9 x G. Ostensen, Morton Grove, AlbinF B D Pl 2,536,356 1/1951 Dager ..271/9 X es 3,273,883 9/1966 Baronnie..271/9 Glaser Arlmgmn 2,235,844 3/1941 Nelson ..271/41 of Ill.

Primary Examiner-Joseph Wegbreit [73] Assignee: SCM Corpor ionAttorney-Pennie, Edmonds, Morton, Taylor and 221 1 11611; Feb. 24, 1971Adams [211 App]. No.: 118,486 [57] ABSTRACT An electrostatic printingmachine having an exposure Related US A li afl n Data station and animaging station, and having copy sheet supply means for the storage ofphotoductive copy Contlnuatlon of 821517, sheets, means for moving acopy sheet from said 1968, abandoned, which is a division of Ser. pplmeans and past the imaging station, and No. 463,071, June 1 l, 1965,Pat. No. vacuum means for holding the copy sheet at the image 3,416,860.station. The machine includes stop means for uncoupling drive means, andbrake means for stopping the movement of the means for moving the copysheet [52] U.S. Cl. ..27l/9, 271/46, 271/74 past the imaging station.The machine also has a [51 Int. Cl. ..B65h 5/02 rality of copy papersheet magazines frgm whieh copy [58] Field of Search ..27l/9, 46, 74sheets may be selectively supplied.

10 Claims, 13 Drawing Figures PATENTEDBEI 17 I972 SHEET 1 BF 4 ZERFAHQRALPH a. OSTE N5EN H Mm Wu 3 m ARTHUR 5.

ALB I N F. BERCXCQRENJJQ RONALD A GLASEE. INVENTOR$ l a Z; f j j MPATENTEDIIBI 11 m2 3.698, 706

SHEET 4 OF 4 STEVEN mmosavxcn ARTHUR s" ZERFAHS RALPH C:- OSTENSEN ALBINF.

BE RGGRE m2. RONALD A.

GrL ASER INVENTORS ELECTROSTATIC PRINTER This application is acontinuation of copending US application Ser. No. 821,517, Oct. 7, 1968,now abandoned which in turn is a division of copending U.S. applicationSer. No. 463,07l,filed June 11, 1965 Pat. No. 3 ,4 I 6,860 forElectrostatic Printer.

This invention relates to photocopy apparatus of the electrostatic type.More particularly it refers to a type of photocopy apparatus wherein anobject desired to be copied may be positioned at a fixed station and thereflected image of the object is projected onto a chargedphotoconductive surface.

In the electrostatic photocopy system used by this invention a uniformelectrostatic charge is first applied to a paper copy sheet having aphotoconductive surface. The image of the subject matter desired to becopied is then projected on to the charged photoconductive surface,selectively discharging the electrostatic charge and reproducing theimage in latent form on the photoconductive surface. Areas of the sheetcorresponding to areas of the original subject matter havingintermediate shade will retain varying proportions of the originalcharge. The latent electrostatic image is then developed by applying tothe photoconductive surface of the copy paper colored particles having acharge opposite in polarity to the charge on the copy paper surface, sothat the particles are attracted to the charged portions of the latentimage to produce a visible image the substantial duplicate of theoriginal. Finally, this visible image is fixed to the paper surface byheat or other suitable means.

Previously, electrostatic photocopies using a photoconductive copy sheethave transported both the original document to be copied and the copysheet simultaneously past object and image windows, respectively, in aprojection station whereby the document is illuminated and projectedline by line on to the copy sheet. Such an apparatus is described in US.patent application Ser. No. 249,248 Photocopy Apparatus, filed Jan. 3,1963 now abandoned, by Ralph G. Ostensen, and assigned to the assigneeof this invention. In such an apparatus the movement of the originaldocument and the copy sheet must be carefully synchronized. Moreover,the original matter to be copied must be a thin, flexible documentcapable of passing through a conveyor belt or roller assembly transportmechanism. This narrows the potential application of such an apparatus,notably eliminating the copying of bound books or bulky periodicals.

The present invention provides an electrostatic photocopier whichprojects the complete image of the original subject matter on to thesurface of a copy sheet at one time, rather than line by line as in theprevious apparatus. By projecting an entire image at one time thesubject document and the copy sheet may be held stationary, and complexsynchronization problems are eliminated. Since the subject document isnot moved during the copying it need not be of any particular form orthickness necessary to pass through rollers or the like; books or otherbulky material may be readily copied.

The invention further provides means for holding a coated copy sheet ina stationary imaging position to receive the entire projected image atone time with no image shielding projection on or in contact with thecoated surface of the copy sheet. A vacuum belt transport system isarranged to transport the coated copy sheet through a portion of thecopy machine on perforated belts without contacting the coated surfaceof the sheet. Means for stopping and starting the perforated belts atpredetermined positions while the copy sheet remains attached to thebelts are also included.

To prevent lateral misregistration of the copy sheet on the perforatedbelts tracking and centering means are provided to retain the belts at aspaced distance apart from one another. A backing member for theperforated belts, including a vacuum platen having an air exhaustingmechanism and having openings in one wall of the platen which mayregister with the openings in the perforated belts to provide a pressuredifferential, serves to secure the copy sheet to the front surface ofthe belts.

Means for aligning the edges of the copy sheet with the image of theedges of the object to be copied are'included in the copying machine. Aplurality of feed magazines to store and selectively distribute varioussizes of copy sheets for use in the copying cycle are provided.Adjustable guides are arranged in the magazines for properly positioningthe various widths of copy sheets, and, in particular, one guide in eachmagazine has two alternate fixed positions while the other guide isadjustable with respect to either of the two fixed positions so as tofix the position of one side edge of the copy sheet relative to themachine.

The magazines are equipped with support means under the copy sheetstacks to centrally engage the underside of each stack near its leadingedge to prevent or inhibit sagging due to the side edges of the stackbeing raised slightly by the guides.

Means are provided for sensing the level or number of copy sheets ineach magazine and for giving a sensible signal when the supply in amagazine is exhausted. Also provided are means for selecting andactivating a feed mechanism in one or another of the magazines, andmeans to prevent activation of the feed mechanism in a particularmagazine if the supply of copy sheets in that magazine is exhausted.

Other and more specific objects of this invention will become more fullyapparent from the following description and appended claims asillustrated by the drawings in which FIG. 1 is a perspective view of theelectrostatic printer showing exposure window and copy sheet magazinecovers raised;

FIG. 2 is an enlarged fragmentary view of the exposure window covermounting mechanism;

FIG. 3 is an enlarged and partially cut away perspective view of thevacuum conveyor belt assembly including the braking mechanism utilizedin stopping the conveyor;

FIG. 4 is a top view of the belt tensioning roller and counterweight;

FIG. 5 is a side view of the belt tensioning roller and counterweight;

FIG. 6 is a sectional view of the printer shown in FIG. 1 substantiallyalong lines 6-6;

FIG. 7 is a perspective view of the paper magazine tray;

FIG. 8 is an enlarged fragmentary cutaway view showing the mounting ofthe support buttons in the magazine tray;

FIG. 9 is an enlarged fragmentary side view of the handle showing itsmounting to the siderail;

FIG. 10 is an enlarged, partially cutaway sectional view of theretention mechanism beneath the right hand side rail of FIG. 7;

FIG. 11 is a partially sectioned side view of the right hand side railand bail in FIG. 7 showing the handle in its arm lowering position;

FIG. 12 is a partially sectioned side view of the left hand side rail ofFIG. 10 showing the handle in its arm raising position;

FIG. 13 is an enlarged view of the friction brake mechanism which islocated beneath the left hand side rail in FIG. 7.

SUMMARY DESCRIPTION Referring now to FIG. 6, the electrostatic printingmachine of the present invention functions as follows:

A document 4 is placed on a window 6 covered with a transparent materialsuch as glass which forms the top wall of a raised box-like portion 8located on the topside of machine housing 2.

The window 6 and document 4 thereon are illuminated by reflector lampassemblies 10 which are mounted in pairs on the side walls of thehousing adjacent portion 8.

The illuminated image of document 4 is reflected by an adjustable mirror12 into a lens 14. Mirror 12 and lens 14 are mounted on a frame 16 whichis in turn adjustably carried by the housing 2. The image is projectedby lens 14 onto an electrostatically charged sheet of photoconductivecopy paper 18, held to vacuum platen 140. As the image strikes the copypaper, the charge on the latter is reduced by an amount corresponding tothe intensity of the image. Dark portions of the image affect the copypaper while light areas of the reflected image may have sufficient lightintensity as to almost completely release the latent electrostaticcharge on the paper.

The copy paper is stored in a paper supply compartment 22 containing twopaper feed trays 24a and 24b. The paper feed trays are constructed toreceive varying widths and lengths of copy paper, allowing the operatorthe flexibility of choosing from one of two sizes stored in the magazineas for example 8 as by 11 inch sheets in one tray and 8 by 14 inch inthe other.

The copy paper is fed to a corona charging unit 26 by either feed roller280 or 28b depending upon which feed tray has been selected for use bythe operator. The actual selection of the feed tray is accomplished bythe actuation of a selector switch which feeds power to one or the otherof the drive mechanism powering feed rollers 28a and 28b. Corona unit 26imparts an electrostatic charge to the photosensitive surface of thecopy paper of approximately 400 volts.

After passing through corona unit 26, the copy paper is transported byperforated conveyor belts 30 over vacuum platen 140 to a predeterminedpoint. At this predetermined point the conveyor belts are stopped andthe image, previously alluded to, is projected onto the copy paper.

The reflector lamp assemblies illuminate the glass window 6 on a timedbasis. At the end of the timing period the conveyor belts arereactivated, causing the copy paper to pass between pivoting guides 226and 228 into a developer station 32 via rollers 202 and 204.

The developer station 32 may be of any well known type, but in thisinstance the paper passes through a pool of liquid developer containingpositively charged particles which are attracted to the charged portionsof the paper to develop the latent electrostatic image which has beenplaced thereon.

After passing through the developer station the copy paper is carried bya conveyor belt 34 beneath heat lamps 38a and 38b which remove anyexcess moisture from the copy paper, and to an exit tray 36 (FIG. I

DETAILED DESCRIPTION As is best seen in FIGS. .1 and 6, housing 2 has abase 38, a pair of supporting side walls 40 extending upwardly from thebase, a front wall 42, and a rear wall 44. Housing 2, as shown in FIG. 1may be provided with removable side panels 46, which shield thefunctional side walls 40 for ornamental purposes.

The top side of housing 2 has raised box-like portion 8 having a window6 covered by a transparent material such as glass. Flexible cover member60 formed of an opaque material is hinged to box 8 and acts as aprotective cover for window 6 when the machine is not in use, and alsomay be used to retain a document on the window 6. When a large documentsurface is placed against window 6, however, it is advantageous to foldback cover 60 to a fully open position. To insure a completely flatcontact between a large document surface and window 6, the hingingarrangement shown in FIG. 2 is utilized. A side portion of box 8 isnotched along most of its length, and a rod 66 fastened at both ends tobox 8 is carried in this notch. Cover member 60 has a reinforced portion64 having a molded groove 68 running its entire length. Cover 60 ismounted onto box 8 by forcing rod 66 into groove 68. By positioning rod66 a spaced distance below the plane of the top window surface 6, cover60 when folded open will be entirely below said window surface plane,thus removing one cause of possible aberration in the optical system ofthe machine.

PAPER FEED MECHANISM A hinged door 70 in the topside of housing 2 asshown in FIG. 1 covers a copy sheet supply compartment 22, wherein copysheets having a photoconductive zinc oxide layer thereon may be storedfor use in the machine. Compartment 22 houses a pair of removable papersupply trays 24a and 24b which may be of identical construction as shownin FIGS. 7 to 13. Trays 24a and 24b comprise flat sheet metal platemembers 74 having turned down lips 76. The trays are mounted one abovethe other in the supply compartment by suitable brackets (not shown) toallow easy removal for loading purposes. In this connection, it shouldbe observed that the lower tray may be mounted to the brackets in a morepermanent manner, as only the top tray is removed in the paper loadingoperation so as to permit access to the lower tray.

As shown in FIG. 7 plate member 74 has a pair of upright paper guides 78slidably mounted thereon to accommodate different widths of paper.

Each guide 78 basically comprises a piece of angle stock having adepending U-shaped foot 80 fastened to the underside edge. Foot 80protrudes through a cutaway portion or slot 82 which extendssubstantially across the entire width of plate 74. A rod 84, carried bytwo tabs (not shown) is inserted through a hole 86 and is positionedcentrally in slot 82 below the level of plate 74. Foot ends 800 and 80beach have a hole therein through which rod 84 is positioned so as toslidingly hold foot 80 to the rod.

As best seen in FIGS. 12 and 13 a friction brake 88 is also provided toinhibit but not prevent sliding movement of guide 78.

Brake 88 comprises a shoe 94 having a rounded slot for engagement withrod 84 and a spring 96 which is carried between shoe 94 and a lip 98 onfoot 80. Spring 96 then urges shoe 94 against the rod providing thedesired braking.

Although both guides can be constructed as described, the preferredembodiment adds a retention mechanism 90 to one guide so as toreleasably fix it in one of two given positions with respect to theoptical system in the machine so as to provide proper registrationbetween the side edge of a document and its projected image on the copypaper respectively as will presently be described. As best seen in FIGS.and 11, an angle bracket 91 has two notches 93a and 93b whichalternately engage one or the other foot ends 80a or 80b. Spring notches93a and 93b hold the guide 78 fairly immobile in either position yet doallow the guide to be moved to the other position by exerting sufficientforce. The bracket 91, however acts as a stop to prevent the guide frommoving any further in either direction.

Thus the guide 78 in FIG. 10 is set in a first position for ordinarycopy sheets, and then adjusted to a second position when running papermaster copy sheets (utilized in offset printing) where a wider margin isdesirable. In either of the two positions a stack of copy sheets may beplaced against the guide and the opposite guide not so retained may beslidably adjusted to engage the opposite edge of the stack, regardlessof the copy sheet width. In the preferred embodiment this adjustment islimited to a minimum proper width of 3 inches and a maximum of 10 inchesfor practical purposes.

Each guide 78 carries an arm 100 pivotally mounted to the guide 78 on ashaft 102. A snap ring 101 on shaft 102 retains the arm to the shaft 102without impairing pivotal movement thereon. Arm 100 is formed with aturned-down front portion 104 which extends downwardly from the arm toslightly overhang the front of plate member 74 and guide 78 so as to actas a front stop for the paper stack as it is loaded into the tray.

Adjacent portion 104 on arm 100 is a finger member 106 positioned tooverlie the corner edge of the paper stack. Finger members 106 assistthe feed rollers 28 in guiding a sheet of paper into the feed systemwithout accidentally carrying the underlying sheets with it.

Obviously, with finger member 106 resting on the paper stack in normaloperation, the arm must be raised slightly when a fresh stack of paperis placed in the tray. This can be manually accomplished by grasping thearm and raising it. Each shaft 102 also carries a handle 1 10 which actsto releasably hold arm 100 in an upright position during loading in amanner which will now be described.

Handle 110 is rotatably carried on shaft 102 but as shown in FIG. 9 itsrotation is inhibited by a spring 103 which bears on a retaining nutattached to the end of shaft 102. Spring 103 then urges the leg portionof handle against retaining ring 101. Any rotation of handle 110 must beagainst the frictional drag developed between the handle 110 and theretaining ring.

I-Iandle 110 is formed with projecting lugs 107 and 108 which act asstops to limit the rotation of the handle 110. As best seen in FIG. 11lug 108 engages an ear 109 or guide 78 when handle 110 is rotatedclockwise toward the front of tray 74.

When the handle 110 is rotated counter-clockwise as shown in FIG. 12 lug107 engages a rearward projection 100a of arm 100 and further rotationpivots the front of the arm, including front portion 107, upwardly.Spring 103, as previously described, acts to inhibit rotation of thehandle 110, therefore the arm 100 remains in an upward position. Whenboth arms have been so raised a new supply of copy sheets may be placedin the tray and the arms lowered again by rotating the handles 1 10forward again as shown in FIG. 1 1.

Due to the thickness of the bottom portion of the guide members, thecenter of the paper stack may tend to bow somewhat, causing feedingproblems. As can be seen in FIGS. 7 and 8 buttons 111 protruding throughopenings in plate 74 are spring biased to lightly engage the undersideof the paper stack to inhibit such bowing.

A collar of shoulder 113 formed on button 111 below a hemisphericalsurface 112 is of a larger diameter than the opening in plate 74 so asto engage the underside of the plate and act as a stop for the upwardmovement of the button. A spring 114 resting on a flange 115 formed onthe side of lip 76 biases the button upwardly toward the stop position.

The hemispherical surface 112 acts as a cam to urge the button 111 belowthe surface of the plate against the spring bias when the guide 78passes over the button 111. Thus, freedom of adjustment of the guides isnot sacrificed by the presence of the buttons.

Returning now to feed rollers 28a and 28b, square drive shafts 29a and29b are employed to respectively mount the rollers 28a and 28b forrotational motion yet allowing lateral adjustment of the rollers 28a and28b on the shafts. Rollers 28a and 28b may be spring loaded to the shaftto prevent unwanted sliding. A suitable drive mechanism can be employedto impart rotation to the shaft such as that described in US.application, Ser. No. 249,248, now abandoned. In the present invention,two such drive mechanisms are used (one for each tray). Additionally, ineach tray a feeler arm 118 (FIG. 6) operationally attached to switches116A or 1163 is provided to sense depletion of the paper stack.Actuation of switch 116A or 1168 upon depletion of the paper causes avisible signal to appear in indicator lamp 516 of Add Paper or the like.Additionally, through circuitry, described in U.S. Pat. No. 3,416,860,issued Dec. 17, 1968, which is incorporated herein, the particular drivemechanism becomes disabled until the paper supply is replenished.

As in application Ser. No. 249,248, now abandoned referred to, anelectro-magnetic clutch is driven through a gear and chain drive whichlikewise powers the other elements in the feed train to be described. Itshould be understood that the aforesaid drive mechanism, which performsa critical synchronization function when image projection is done withboth document and copy paper moving, is not as critical in thisinvention because the image projection is done when both subject matterand copy paper are in nonmoving positions.

The copy paper, fed by either feed rollers 28a or 28b, is urged toward athroat formed by rollers 120 and 122. Roller 120 has a fairly largediameter and therefore can function also as a guide for changing thedirection of the paper travel. This is accomplished in cooperation witha curved guide 126 which is located immediately beyond roller 122. Guide126 is shaped to approximately the same radius of curvature as roller120 to allow smooth transit of the paper therebetween.

The throat or bite of rollers 120 and 122 is vertically positioned so asto operate equally well with copy paper fed to it from either tray. Inthis connection also, the large diameter of roller 120 is of assistance.

Immediately adjacent guide 126, roller 124 is positioned to receive thecopy paper and in cooperation with roller 120, urge the paper toward thecorona charging station 26.

As the paper passes between guide 126 and roller 120, a trip lever 128is engaged by the paper edge, which in turn, operates a switch 130.Switch 130, among other things, actuates circuitry to turn on the coronacharging unit 26.

Corona charging unit 26 as best seen in FIG. 6 comprises a pair ofrectangular shields 27 each housing a set of very small diameter coronawires 25, so named because of the corona discharge created when avoltage in the order of 4 to 8 kilovolts is applied to them. For a morecomplete description of the construction and operation of such a unitattention is again invited to application Ser. No. 249,248, nowabandoned. The copy sheet passes between the sets of wires and itsphotosensitive surface becomes negatively charged by the corona ioncloud therein.

VACUUM CONVEYOR SYSTEM After passing through the corona charging unit26, the copy sheet is picked up and transported by perforated conveyorbelts 30. Referring to FIGS. 3 5, it will be seen that three such beltsare carried side by side between top roller 132 and bottom roller 134.The belts may be constructed of Mylar or similar material, the mainrequirements being flexibility and strength. As can be seen in FIG. 3,the belts are perforated by many small, closely spaced holes 136 toallow air to pass therethrough.

Between the two portions of the belt loops, a rectangular vacuum platenor chamber 140 having a series of oval openings 142 on its frontsurface, cooperates with the perforations 136 in the belts 30. Platen140 is formed as a shallow box having an exhaust or vacuum fan 144connected thereto.

Air is drawn in through the belt holes 136, the platen openings 142, andtravels through the platen 140 to fan 144. Appropriate baffling (notshown) within the platen 140 insures an even flow of air through all theopenings.

The copy sheet, upon reaching the belts 30, is drawn and held to thebelts 30 by the pressure differential developed across the belt 30 asthe air is pulled into the platen 140 through the perforated openings.

Returning now to the mounting of the belts 30, a tensioning rollersystem is located behind the platen 140, acting to provide tension onthe belts 30 and to aid in proper tracking of the belts 30 and toprevent lateral wander. This is of particular importance in the machineof this invention because any lateral travel of the belts could alsoshift the copy sheet, causing misregistration as the image of thedocument is projected thereupon.

An idler roller 146 is therefore provided which extends through thebeltss loops bowing them outwardly. Roller 146 is carried by sidewalls40 of housing 2 in similar fashion to rollers 132 and 134.Counterweighted rollers 152 are provided for each belt 30, and as bestseen in FIG. 4 engages the center of each belt 30. The axial roundednessof roller 152, together with its central engagement of the beit 30causes a lateral bowing of the belt 30 which, it has been found, acts toprevent lateral wander of the belt 30. In this connection it should benoted that upper roller 132 can also be provided with rounded or crownedportions to centrally engage each belt if necessary.

Weighted roller 152 is carried by a bracket 154, which has attachedthereto at its opposite extremity a weight 156 which comprises a groupof weights having various masses. Bracket 154 is in turn pivotallyattached at 158 to rod 160, which is horizontally carried betweensidewalls 40. Each belt 30 is provided with such a weighted rollerassembly and the weight on each can be adjusted by varying the number ofweights used for maximum results.

In addition to the tracking or anti-wander effect of the weighted roller1S2, circular separators or spacers 167 are provided between the belts30 and secured in any suitable manner on bottom roller 134 of theconveyor belt assembly. Spacers 167 are of a diameter to protrude beyondthe belts 30 and thereby provide rounded protrusions at the bottom ofthe conveyor belt assembly which perform a primary function as copysheet removal members. Thus the moving copy sheet upon reaching theseparators is carried away from the belts and the pressure differentialeffects of the perforations therein.

Still referring to FIG. 3, a trip lever 162 is shown projecting betweenthe belts 30 at a point below the bottom of the platen 140 and isattached to an electrical switch mechanism 164. When a copy sheettraveling with the belts 30 reaches this point, lever 162 is carried bythe sheet to a switch tripping position (not shown). At this point,switch 164 is actuated, causing, through an electrical circuit describedin [1.8. Pat. 3,416,860, issued Dec. 17, 1968 the conveyor belts tostop. The alluded to circuitry controls an electromagnetic clutch (notshown) which provides driving power to upper roller 132 from the gearand chain drive mechanism of application Ser. No. 249,248, nowabandoned, previously referred to. Thus, engagement of the trip leverdeactivates the drive train to the conveyor. In this connection, stillreferring to FIG. 3, it should be noted that switch mechanism 164 ismounted to an adjustable bracket 166 which is in turn mounted tosidewall 40 by bolts 168 carried in slots 170 in the sidewall. The Thebracket 166, switch 164 and lever 162 can thus be vertically adjusted soas to engage the copy sheet at different points. The adjustment, whichneed only be made upon initial construction, serves to locate the bottomedge of the copy sheet with respect to the projected image. Thisrelationship can be readily appreciated by referring to the projectedimages shown in FIG. 20 of U.S. Pat. No. 3,416,860. As shown in thatfigure, the front edge 200a of the exposure window 6 and document 4thereon becomes, due to the optical system, edge 200 b on the copysheet. If the sheet has progressed beyond this point, the projectedimage will be spaced from the edge of the copy sheet. If the documentand copy sheet are of identical size, the opposite edge of the documentwill be projected beyond the corresponding opposite edge of the copysheet. The registration between document and copy sheet thus plays animportant role in proper performance.

In this same connection it should be noted that the side edge 201a ofexposure window 6 and document 4 are projected onto the copy sheet at201b due to the optical reversal. Positioning of the copy sheet at 201bis accomplished by proper setting of the side rail 100 or guideretention mechanism previously described.

While the initial adjustment of the position of trip lever 162 to alarge extent controls the vertical registration, there still exists thepossibility of slight overrun due to the momentum of the rollers andbelts. For this reason, an additional registration safeguard is builtinto the system in the form of a brake mechanism.

Referring again to FIG. 3, it will be seen that upper roller 132 carriesa large disc 172 on one end. A brake band 174, wrapped around the dischas a first end 180 attached to a lever 182 by pin 184. Lever 182 inturn is pivotally attached to sidewall 40 by a pin 186 at 190. The otherend of the brake band 188 is likewise attached to sidewall 40 by pin186. A spring 176, attached to lever 182 and to a bracket 192 mounted tosidewall 40, urges lever 182 downward, carrying brake band end 180 withlever, to effect a braking action against the periphery of disc 172. Thenormal position of the mechanism is therefore in a braking position.

To release the brake mechanism described, a solenoid 194, mounted tosidewall 40 adjacent bracket 192, has a plunger 196 attached to the endof lever 182 at pivot point 198.

Under normal conditions, the spring 176 pulling lever 182 downwardlyalso carries plunger 196 with it. When solenoid 194 is activated, theplunger and lever are raised, overcoming the spring 176 and causing thebrake band 174 to release.

The activation of solenoid 194 is accomplished simultaneously withenergization of the electromagnetic clutch on the conveyor belt byelectrically wiring the solenoid and clutch in parallel. Thus, the copysheet in tripping lever 162 not only shuts off the driving means for theconveyor belt, but causes the belt to instantly stop by application ofthe brake mechanism 174 to roller 132.

The copy sheet, after contacting lever 162, is held to the belts 30 in astationary position. The image of the document to be copied is thenprojected onto the copy sheet for a fixed increment of time sufficientto selectively discharge the areas of the copy sheet corresponding tothe lighter areas of the document, leaving a charge pattern on thephotoconductive surface of the copy sheet as is well known in the fieldof electrophotography.

After the image exposure period, the conveyor belts 30 are reactivatedand the brake 174 released, allowing the copy sheet to pass beyond thetrip lever 162 and be engaged by the spacers 162. As previouslydescribed, the spacers 167 now assist in removing the sheet from theinfluence of the pressure differential of the perforated belts 30 andvacuum platen 140.

The copy sheet next passes to the developer station 32 (FIGS. 6 and)which comprises a pair of entrance rollers 202 and 204. Upper roller 202may be a steel roller carried by the sidewalls 40 through insulatedbearings. Lower roller 204 may have a rubber surface to provide goodfrictional contact with the copy sheet for driving purposes.

Beyond the entrance rollers in the developer station, the copy sheetpasses through a pool of liquid developer containing positively chargedcolored particles which are attracted to the remaining negativelycharged portions of the copy sheet corresponding to the dark portions ofthe image which has been projected thereon.

After passing through the pool of liquid developer, the copy sheet isengaged by a second set of rollers 206 and 208 which not only serve topropel the developed copy sheet onward in the feed train, but alsoperform a wringer or squeegee function. The copy sheet, as it emergesfrom the pool of liquid developer, has a film of liquid adhering to itssurface. Since it is desirous to have a dry copy sheet as the finalproduct of the machine, this wet film must be removed. Rollers 206 and208 serve to remove most of this liquid film.

As with entrance rollers 202 and 204, the exit rollers may comprise anupper steel roller 206 and a lower rubber roller 208. In the preferredembodiment, the upper steel roller 206 is electrically grounded to thehousing while the lower roller 208 is insulated therefrom by insulatedbearings. Both rollers 206 and 208 are carried by the sidewalls 40 insimilar fashion to rollers 202 and 204.

After passing through exit rollers 206 and 208, the carrier sheet ispicked up by a conveyor belt 34 and delivered to exit tray 36. Conveyorbelt 34 comprises a pair of rollers 210 and 212 journaled in appropriatebearings in sidewalls 40 and having a series of spaced apart cords orbands 214 which can be of an elastic type material. The conveyor belt 34is powered through an appropriate spur gear (not shown) to the drivechain previously referred to.

Positioned above the conveyor 34 are a pair of heat lamps 38a and 38b.Any moisture remaining on the copy sheet is removed by the heat lamps,in conjunction with a fan 220 which circulates the warm air above andbeneath the copy sheet between the spaced apart cords.

The foregoing description and drawings should be considered asillustrative of preferred embodiments and that changes and modificationsmay be made without departing from the scope of the invention asmeasured by the appended claims.

What is claimed is:

1. In a photocopying machine having an imaging station for exposing alight-sensitive copy sheet to a projected image while the copy sheet ismaintained stationary, the combination comprising endless belt means forcarrying a light-sensitive copy sheet past the f imaging station,mounting means for mounting said endless belt means for movement in asubstantially straight line past the imaging station, said mountingmeans including two spaced shaft means rotatably supported in spacedapart relation and parallel to each other, drive means releasablycoupled to one of said shaft means for driving said shaft means to movesaid endless belt means past the imaging station, means to impart apressure differential onto the light-sensitive copy sheet beingtransported past the imaging station to hold the copy sheet on saidendless belt means, stop means adjacent said endless belt means andoperable in response to engagement by the copy sheet at the imagingstation for releasing the coupling of said drive means to said shaftmeans, and brake means operable on one of said shaft means in responseto the operation of said stop means for stopping the movement of saidendless belt means past the imaging station to accurately position acopy sheet at the imaging station.

2. A photocopying machine according to claim 1, wherein said means toimpart a pressure differential onto the light-sensitive copy sheetcomprises means defining a vacuum chamber located between said spacedshaft means and inside the endless belt means carried by said shaftmeans, said means defining said vacuum chamber including a surfaceextending substantially parallel with the endless belts at the imagingstation with perforations formed therein and opening toward said imagingstation to enable air to be drawn therethrough to hold a light-sensitivecopy sheet against said endless belt means, and said endless belt meanshaving perforations formed therein to enable air to flow therethroughinto said vacuum chamber.

3. A photocopying machine according to claim 2, wherein said mountingmeans are arranged for mounting said endless belt means formovement pasta generally vertical imaging station with one of said shaft means beinglocated beneath said means defining a vacuum chamber, said drive meansbeing releasably coupled to said shaft means located beneath said vacuumchamber means, said other shaft means being located above said vacuumchamber means, and said brake means being operable on said other shaftmeans.

4. A photocopying machine according to claim 3, the combination furthercomprising removal means carried by said shaft means located beneathsaid vacuum chamber means for urging the copy sheet being carried bysaid endless belts away from the perforated surface of said endless beltmeans.

5. An electrostatic photocopy machine having an exposure station and acopy sheet imaging station spaced from said exposure station, and avacuum sheet transport assembly of the type wherein a pressuredifferential is utilized to retain a sheet member against a backingmember comprising:

a. a housing member in said machine;

b. a vacuum chamber carried by said housing and having a perforatedfront plate thereon;

0. means for feeding a copy sheet toward said chamber;

d. drive means on said housing, including a drive roller positionedabove the chamber and a driven 6 the perforated front plate of saidvacuum chamber;

f. adjustable stop means positioned between said belts and engaged bythe leading edge of said copy sheet to disengage the drive means;

. brake means activated by said stop means and engaging said driveroller to prevent overtravel of said copy sheet after contact with saidstop means, said brake means cooperating with said adjustable stop meansto provide an accurate positioning of said copy sheet in front of saidvacuum chamber; and

h. removal means carried by said driven roller between the belts to urgesaid sheet member away from said belts.

6. [n a photocopying machine capable of handling different iengths oflight-sensitive copy sheets, the combination comprising a magazine forcontaining a supply of copy paper sheets, another magazine forcontaining another supply of copy paper sheets, each of said magazineshaving a floor therein and a pair of adjustable side rails slidablyassociated therewith and having detent means associated with said floorto locate one of said side rails in one of two given positions, at leastone of said magazines being removable from said photocopying machine forreplenishing the supply of copy paper sheets in said magazines, sheetfeeding means associated with each of said magazines including a pair offeed rollers adjustably mounted on a shaft having a polygonalcross-section for feeding the topmost sheet in each of said magazinesinto the photocopying machine, and means for selectively activating oneof said sheet feeding means for supplying sheets from one of saidmagazines into said photocopying machine.

7. A photocopying machine according to claim 6, the combination furthercomprising copy sheet level sensing means associated with each of saidmagazines for sensing the height of the supply of copy sheets in each ofsaid magazines, and said copy sheet level sensing means being operablein response to the supply of copy sheets in one of said magazinesdiminishing beneath a given height for selectively deactivating theparticular copy sheet feeding means associated with that magazine andfor providing a visual signal.

8. In a photocopying machine capable of handling different lengths oflight-sensitive copy sheets, the combination comprising a magazine forcontaining a supply of copy paper sheets, sheet feeding means associatedwith said magazine for feeding the topmost sheet in said magazine intothe photocopying machine, another magazine for containing another supplyof copy paper sheets, another sheet feeding means associated with saidother magazine for feeding the topmost sheet in said magazine into thephotocopying machine, and means for selectively activating one of saidsheet feeding means for supplying sheets from one of said magazines intosaid photocopying machine, and further comprising support means carriedby each of said magazines for centrally engaging the underside of theleading sheet of a stack of copy paper sheets placed therein.

9. ln an electrostatic printing machine capable of handling varioussizes of copy sheet material:

a. a plurality of copy sheet feed magazines, each of magazines having afloor therein and a pair of adjustable side rails slidably associatedtherewith;

b. detent means associated with said floor to locate deactivate therespective copy sheet feed means one of said side rails in one of twogiven positions when said copy sheet supply in that magazine withrespect to said magazine floor', diminishes below a give height; and

c. sheet feed means associated with each magazine f- Sheet engagingmeans carried by said side rails including a pair of feed rollers whichcontact the above the floor for engaging the front edges of said topsheet of a copy sheet stack to f d th to copy sheets to inhibit doublefeeding of copy sheet of said stack into the printing machine; Sheetsd.means for selectively activating one of said sheet An electrostatic P tmachine according to feed means; claim 9 having support means carried byeach said e. copy sheet level sensing means associated with 10 magftzinefloor to centrally engage theundetside f the Said magazines to sense theheight f the copy leading edge ofastack of copy sheets placed therein.sheet supply in each magazine and to selectively

1. In a photocopying machine having an imaging station for exposing a light-sensitive copy sheet to a projected image while the copy sheet is maintained stationary, the combination comprising endless belt means for carrying a light-sensitive copy sheet past the imaging station, mounting means for mounting said endless belt means for movement in a substantially straight line past the imaging station, said mounting means including two spaced shaft means rotatably supported in spaced apart relation and parallel to each other, drive means releasably coupled to one of said shaft means for driving said shaft means to move said endless belt means past the imaging station, means to impart a pressure differential onto the light-sensitive copy sheet being transported past the imaging station to hold the copy sheet on said endless belt means, stop means adjacent said endless belt means and operable in response to engagement by the copy sheet at the imaging station for releasing the coupling of said drive means to said shaft means, and brake means operable on one of said shaft means in response to the operation of said stop means for stopping the movement of said endless belt means past the imaging station to accurately position a copy sheet at the imaging station.
 2. A photocopying machine according to claim 1, wherein said means to impart a pressure differential onto the light-sensitive copy sheet comprises means defining a vacuum chamber located between said spaced shaft means and inside the endless belt means carried by said shaft means, said means defining said vacuum chamber including a surface extending substantially parallel with the endless belts at the imaging station with perforations formed therein and opening toward said imaging station to enable air to be drawn therethrough to hold a light-sensitive copy sheet against said endless belt means, and said endless belt means having perforations formed therein to enable air to flow therethrough into said vacuum chamber.
 3. A photocopying machine according to claim 2, wherein said mounting means are arranged for mounting said endless belt means for movement past a generally vertical imaging station with one of said shaft means being located beneath said means defining a vacuum chamber, said drive means being releasably coupled to said shaft means located beneath said vacuum chamber means, said other shaft means being located above said vacuum chamber means, and said brake means being operable on said other shaft means.
 4. A photocopying machine according to claim 3, the combination further comprising removal means carried by said shaft means located beneath said vacuum chamber means for urging the copy sheet being carried by said endless belts away from the perforated surface of said endless belt means.
 5. An electrostatic photocopy machine having an exposure station and a copy sheet imaging station spaced from said exposure station, and a vacuum sheet transport assembly of the type wherein a pressure differential is utilized to retain a sheet member against a backing member comprising: a. a housing member in said machine; b. a vacuum chamber carried by said housing and having a perforated front plate thereon; c. means for feeding a copy sheet toward said chamber; d. drive means on said housing, including a drive roller positioned above the chamber and a driven roller positioned below the chamber; e. spaced apart perforated belts interconnecting said rollers, said belts being positioned to pass across the perforated front plate of said vacuum chamber; f. adjustable stop means positioned between said belts and engaged by the leading edge of said copy sheet to disengage the drive means; g. brake means activated by said stop means and engaging said drive roller to prevent overtravel of said copy sheet after contact with said stop means, said brake means cooperating with said adjustable stop means to provide an accurate positioning of said copy sheet in front of said vacuum chamber; and h. removal means carried by said driven roller between the belts to urge said sheet member away from said belts.
 6. In a photocopying machine capable of handling different lengths of light-sensitive copy sheets, the combination comprising a magazine for containing a supply of copy paper sheets, another magazine for containing another supply of copy paper sheets, each of said magazines having a floor therein and a pair of adjustable side rails slidably associated therewith and having detent means associated with said floor to locate one of said side rails in one of two given positions, at least one of said magazines being removable from said photocopying machine for replenishing the supply of copy paper sheets in said magazines, sheet feeding means associated with each of said magazines including a pair of feed rollers adjustably mounted on a shaft having a polygonal cross-section for feeding the topmost sheet in each of said magazines into the photocopying machine, and means for selectively activating one of said sheet feeding means for supplying sheets from one of said magazines into said photocopying machine.
 7. A photocopying machine according to claim 6, the combination further comprising copy sheet level sensing means associated with each of said magazines for sensing the height of the supply of copy sheets in each of said magazines, and said copy sheet level sensing means being operable in response to the supply of copy sheets in One of said magazines diminishing beneath a given height for selectively deactivating the particular copy sheet feeding means associated with that magazine and for providing a visual signal.
 8. In a photocopying machine capable of handling different lengths of light-sensitive copy sheets, the combination comprising a magazine for containing a supply of copy paper sheets, sheet feeding means associated with said magazine for feeding the topmost sheet in said magazine into the photocopying machine, another magazine for containing another supply of copy paper sheets, another sheet feeding means associated with said other magazine for feeding the topmost sheet in said magazine into the photocopying machine, and means for selectively activating one of said sheet feeding means for supplying sheets from one of said magazines into said photocopying machine, and further comprising support means carried by each of said magazines for centrally engaging the underside of the leading sheet of a stack of copy paper sheets placed therein.
 9. In an electrostatic printing machine capable of handling various sizes of copy sheet material: a. a plurality of copy sheet feed magazines, each of magazines having a floor therein and a pair of adjustable side rails slidably associated therewith; b. detent means associated with said floor to locate one of said side rails in one of two given positions with respect to said magazine floor; c. sheet feed means associated with each magazine including a pair of feed rollers which contact the top sheet of a copy sheet stack to feed the top sheet of said stack into the printing machine; d. means for selectively activating one of said sheet feed means; e. copy sheet level sensing means associated with said magazines to sense the height of the copy sheet supply in each magazine and to selectively deactivate the respective copy sheet feed means when said copy sheet supply in that magazine diminishes below a give height; and f. sheet engaging means carried by said side rails above the floor for engaging the front edges of said copy sheets to inhibit double feeding of copy sheets.
 10. An electrostatic printing machine according to claim 9 having support means carried by each said magazine floor to centrally engage the underside of the leading edge of a stack of copy sheets placed therein. 